Radharani Alyana 1*, Girija Ra jaram1, Jatin
Rathod1 ,
A. Chandrasekhar Reddy1 , D. S.
Misra1 , C. G.
Patil2 and M. Y. S. Prasad3
1 CSRE, IIT-B, Powai, Mumbai 400 076, India
2 MCF-ISRO, PB #66, Hassan, Karnataka State 573201, India
3
SITAA-SAC, ISRO. Ahmedabad, Gujarat State 380015, India
Abstract. As part of study of RED (Relativistic Electron Dropout) events at Geostationary orbit, we have classified them on the basis of their solar causes. We find that the solar causes associated with RED events are Interplanetary (IP) Shocks, Coronal Mass Ejection (CME), Flares, Magnetic Clouds and Coro- tating Interaction Regions (CIR) followed by Coronal Hole (CH) stream. Here we have taken CME and CH associated RED events during 2005. We have studied Interplanetary parameters (IP) (i.e. solar wind Velocity (Vsw), solar wind Ion density (Nsw), solar wind dynamic pressure (Psw ), total Interplan- etary magnetic field B along with its north-south component, Bz), Radiation belt (RB) parameters at geostationary orbit (i.e. electron flux >2 MeV, Hp component (i.e. the component of magnetic field parallel to the spin axis of the satellite) and dayside magnetopause distance (MP)) and the geomagnetic indices (i.e. Dst and Kp) and Cosmic Ray Neutron Monitor (CRNM) count. The parameters which show significant differences between CME and CH events are Vsw, Psw, B, Bz, Dst and Kp, with Vsw and Dst showing the largest dif- ferences. As typical examples, in the case of the CME of 22 January, 2005, Vsw touches over 975 km s-1 and Dst is Sudden Storm Commencement (SSC) type with minimum Dst being -110 nT . In the case of the CH of 05 April, Vsw is only 650 km s-1 and Dst is of Gradual Commencement (GC) type with minimum Dst of -80 nT. In this paper we present differences observed in the above mentioned parameters for several RED events associated with CME and CH during 2005.
Keywords: Sun : coronal holes - CME - solar-terrestrial relations